Re: [Discuss-gnuradio] simple mod-demod combinations doesn't work

[Sylvain Munaut]

> If i start an audio flow graph without [throttle] and increase some additive
> noise or change the volume with a multiplier in the stream the audible
> signal gets effected way too slow (action-to-effect-time approximately 10 s
> or more). If I use a [throttle] after the [wav file source] i can effect the
> stream directly - maybe i can call it "in real time", but then sometimes aU
> occurs.
>
> The issue remains also if i use real hardware (redpitaya with osmocom
> blocks) an resampler blocks in the stream.

That's because of buffering. Each block has a buffer after it and if
your "hardware" is at the end of the chain, then all the elements
before it are free to generate data in advance until they fill all
those buffers (the more blocks the more buffers). And so any change to
those source will only be applied after all the pre-generated data
that's sitting in the buffers has been flushed.

The default size of those buffer might not be appropriate for low rate
audio because they can easily represent seconds ...

> So is the solution for such problems a tagged stream with control through
> tags or the usage of PDUs?

No.
The easiest solution is to manually control the max size of the
buffers for the "low rate" blocks in your chains to prevent too much
buffering there.


Cheers,

    Sylvain